/**
 * Port from https://github.com/mapbox/earcut (v2.2.2)
 */

const Earcut = {
  triangulate: function (data, holeIndices, dim) {
    dim = dim || 2

    const hasHoles = holeIndices && holeIndices.length
    const outerLen = hasHoles ? holeIndices[0] * dim : data.length
    let outerNode = linkedList(data, 0, outerLen, dim, true)
    const triangles = []

    if (!outerNode || outerNode.next === outerNode.prev) return triangles

    let minX, minY, maxX, maxY, x, y, invSize

    if (hasHoles) outerNode = eliminateHoles(data, holeIndices, outerNode, dim)

    // if the shape is not too simple, we'll use z-order curve hash later; calculate polygon bbox
    if (data.length > 80 * dim) {
      minX = maxX = data[0]
      minY = maxY = data[1]

      for (let i = dim; i < outerLen; i += dim) {
        x = data[i]
        y = data[i + 1]
        if (x < minX) minX = x
        if (y < minY) minY = y
        if (x > maxX) maxX = x
        if (y > maxY) maxY = y
      }

      // minX, minY and invSize are later used to transform coords into integers for z-order calculation
      invSize = Math.max(maxX - minX, maxY - minY)
      invSize = invSize !== 0 ? 1 / invSize : 0
    }

    earcutLinked(outerNode, triangles, dim, minX, minY, invSize)

    return triangles
  },
}

// create a circular doubly linked list from polygon points in the specified winding order
function linkedList(data, start, end, dim, clockwise) {
  let i, last

  if (clockwise === signedArea(data, start, end, dim) > 0) {
    for (i = start; i < end; i += dim) last = insertNode(i, data[i], data[i + 1], last)
  } else {
    for (i = end - dim; i >= start; i -= dim) last = insertNode(i, data[i], data[i + 1], last)
  }

  if (last && equals(last, last.next)) {
    removeNode(last)
    last = last.next
  }

  return last
}

// eliminate colinear or duplicate points
function filterPoints(start, end) {
  if (!start) return start
  if (!end) end = start

  let p = start,
    again
  do {
    again = false

    if (!p.steiner && (equals(p, p.next) || area(p.prev, p, p.next) === 0)) {
      removeNode(p)
      p = end = p.prev
      if (p === p.next) break
      again = true
    } else {
      p = p.next
    }
  } while (again || p !== end)

  return end
}

// main ear slicing loop which triangulates a polygon (given as a linked list)
function earcutLinked(ear, triangles, dim, minX, minY, invSize, pass) {
  if (!ear) return

  // interlink polygon nodes in z-order
  if (!pass && invSize) indexCurve(ear, minX, minY, invSize)

  let stop = ear,
    prev,
    next

  // iterate through ears, slicing them one by one
  while (ear.prev !== ear.next) {
    prev = ear.prev
    next = ear.next

    if (invSize ? isEarHashed(ear, minX, minY, invSize) : isEar(ear)) {
      // cut off the triangle
      triangles.push(prev.i / dim)
      triangles.push(ear.i / dim)
      triangles.push(next.i / dim)

      removeNode(ear)

      // skipping the next vertex leads to less sliver triangles
      ear = next.next
      stop = next.next

      continue
    }

    ear = next

    // if we looped through the whole remaining polygon and can't find any more ears
    if (ear === stop) {
      // try filtering points and slicing again
      if (!pass) {
        earcutLinked(filterPoints(ear), triangles, dim, minX, minY, invSize, 1)

        // if this didn't work, try curing all small self-intersections locally
      } else if (pass === 1) {
        ear = cureLocalIntersections(filterPoints(ear), triangles, dim)
        earcutLinked(ear, triangles, dim, minX, minY, invSize, 2)

        // as a last resort, try splitting the remaining polygon into two
      } else if (pass === 2) {
        splitEarcut(ear, triangles, dim, minX, minY, invSize)
      }

      break
    }
  }
}

// check whether a polygon node forms a valid ear with adjacent nodes
function isEar(ear) {
  const a = ear.prev,
    b = ear,
    c = ear.next

  if (area(a, b, c) >= 0) return false // reflex, can't be an ear

  // now make sure we don't have other points inside the potential ear
  let p = ear.next.next

  while (p !== ear.prev) {
    if (pointInTriangle(a.x, a.y, b.x, b.y, c.x, c.y, p.x, p.y) && area(p.prev, p, p.next) >= 0) return false
    p = p.next
  }

  return true
}

function isEarHashed(ear, minX, minY, invSize) {
  const a = ear.prev,
    b = ear,
    c = ear.next

  if (area(a, b, c) >= 0) return false // reflex, can't be an ear

  // triangle bbox; min & max are calculated like this for speed
  const minTX = a.x < b.x ? (a.x < c.x ? a.x : c.x) : b.x < c.x ? b.x : c.x,
    minTY = a.y < b.y ? (a.y < c.y ? a.y : c.y) : b.y < c.y ? b.y : c.y,
    maxTX = a.x > b.x ? (a.x > c.x ? a.x : c.x) : b.x > c.x ? b.x : c.x,
    maxTY = a.y > b.y ? (a.y > c.y ? a.y : c.y) : b.y > c.y ? b.y : c.y

  // z-order range for the current triangle bbox;
  const minZ = zOrder(minTX, minTY, minX, minY, invSize),
    maxZ = zOrder(maxTX, maxTY, minX, minY, invSize)

  let p = ear.prevZ,
    n = ear.nextZ

  // look for points inside the triangle in both directions
  while (p && p.z >= minZ && n && n.z <= maxZ) {
    if (p !== ear.prev && p !== ear.next && pointInTriangle(a.x, a.y, b.x, b.y, c.x, c.y, p.x, p.y) && area(p.prev, p, p.next) >= 0) return false
    p = p.prevZ

    if (n !== ear.prev && n !== ear.next && pointInTriangle(a.x, a.y, b.x, b.y, c.x, c.y, n.x, n.y) && area(n.prev, n, n.next) >= 0) return false
    n = n.nextZ
  }

  // look for remaining points in decreasing z-order
  while (p && p.z >= minZ) {
    if (p !== ear.prev && p !== ear.next && pointInTriangle(a.x, a.y, b.x, b.y, c.x, c.y, p.x, p.y) && area(p.prev, p, p.next) >= 0) return false
    p = p.prevZ
  }

  // look for remaining points in increasing z-order
  while (n && n.z <= maxZ) {
    if (n !== ear.prev && n !== ear.next && pointInTriangle(a.x, a.y, b.x, b.y, c.x, c.y, n.x, n.y) && area(n.prev, n, n.next) >= 0) return false
    n = n.nextZ
  }

  return true
}

// go through all polygon nodes and cure small local self-intersections
function cureLocalIntersections(start, triangles, dim) {
  let p = start
  do {
    const a = p.prev,
      b = p.next.next

    if (!equals(a, b) && intersects(a, p, p.next, b) && locallyInside(a, b) && locallyInside(b, a)) {
      triangles.push(a.i / dim)
      triangles.push(p.i / dim)
      triangles.push(b.i / dim)

      // remove two nodes involved
      removeNode(p)
      removeNode(p.next)

      p = start = b
    }

    p = p.next
  } while (p !== start)

  return filterPoints(p)
}

// try splitting polygon into two and triangulate them independently
function splitEarcut(start, triangles, dim, minX, minY, invSize) {
  // look for a valid diagonal that divides the polygon into two
  let a = start
  do {
    let b = a.next.next
    while (b !== a.prev) {
      if (a.i !== b.i && isValidDiagonal(a, b)) {
        // split the polygon in two by the diagonal
        let c = splitPolygon(a, b)

        // filter colinear points around the cuts
        a = filterPoints(a, a.next)
        c = filterPoints(c, c.next)

        // run earcut on each half
        earcutLinked(a, triangles, dim, minX, minY, invSize)
        earcutLinked(c, triangles, dim, minX, minY, invSize)
        return
      }

      b = b.next
    }

    a = a.next
  } while (a !== start)
}

// link every hole into the outer loop, producing a single-ring polygon without holes
function eliminateHoles(data, holeIndices, outerNode, dim) {
  const queue = []
  let i, len, start, end, list

  for (i = 0, len = holeIndices.length; i < len; i++) {
    start = holeIndices[i] * dim
    end = i < len - 1 ? holeIndices[i + 1] * dim : data.length
    list = linkedList(data, start, end, dim, false)
    if (list === list.next) list.steiner = true
    queue.push(getLeftmost(list))
  }

  queue.sort(compareX)

  // process holes from left to right
  for (i = 0; i < queue.length; i++) {
    eliminateHole(queue[i], outerNode)
    outerNode = filterPoints(outerNode, outerNode.next)
  }

  return outerNode
}

function compareX(a, b) {
  return a.x - b.x
}

// find a bridge between vertices that connects hole with an outer ring and and link it
function eliminateHole(hole, outerNode) {
  outerNode = findHoleBridge(hole, outerNode)
  if (outerNode) {
    const b = splitPolygon(outerNode, hole)

    // filter collinear points around the cuts
    filterPoints(outerNode, outerNode.next)
    filterPoints(b, b.next)
  }
}

// David Eberly's algorithm for finding a bridge between hole and outer polygon
function findHoleBridge(hole, outerNode) {
  let p = outerNode
  const hx = hole.x
  const hy = hole.y
  let qx = -Infinity,
    m

  // find a segment intersected by a ray from the hole's leftmost point to the left;
  // segment's endpoint with lesser x will be potential connection point
  do {
    if (hy <= p.y && hy >= p.next.y && p.next.y !== p.y) {
      const x = p.x + ((hy - p.y) * (p.next.x - p.x)) / (p.next.y - p.y)
      if (x <= hx && x > qx) {
        qx = x
        if (x === hx) {
          if (hy === p.y) return p
          if (hy === p.next.y) return p.next
        }

        m = p.x < p.next.x ? p : p.next
      }
    }

    p = p.next
  } while (p !== outerNode)

  if (!m) return null

  if (hx === qx) return m // hole touches outer segment; pick leftmost endpoint

  // look for points inside the triangle of hole point, segment intersection and endpoint;
  // if there are no points found, we have a valid connection;
  // otherwise choose the point of the minimum angle with the ray as connection point

  const stop = m,
    mx = m.x,
    my = m.y
  let tanMin = Infinity,
    tan

  p = m

  do {
    if (hx >= p.x && p.x >= mx && hx !== p.x && pointInTriangle(hy < my ? hx : qx, hy, mx, my, hy < my ? qx : hx, hy, p.x, p.y)) {
      tan = Math.abs(hy - p.y) / (hx - p.x) // tangential

      if (locallyInside(p, hole) && (tan < tanMin || (tan === tanMin && (p.x > m.x || (p.x === m.x && sectorContainsSector(m, p)))))) {
        m = p
        tanMin = tan
      }
    }

    p = p.next
  } while (p !== stop)

  return m
}

// whether sector in vertex m contains sector in vertex p in the same coordinates
function sectorContainsSector(m, p) {
  return area(m.prev, m, p.prev) < 0 && area(p.next, m, m.next) < 0
}

// interlink polygon nodes in z-order
function indexCurve(start, minX, minY, invSize) {
  let p = start
  do {
    if (p.z === null) p.z = zOrder(p.x, p.y, minX, minY, invSize)
    p.prevZ = p.prev
    p.nextZ = p.next
    p = p.next
  } while (p !== start)

  p.prevZ.nextZ = null
  p.prevZ = null

  sortLinked(p)
}

// Simon Tatham's linked list merge sort algorithm
// http://www.chiark.greenend.org.uk/~sgtatham/algorithms/listsort.html
function sortLinked(list) {
  let i,
    p,
    q,
    e,
    tail,
    numMerges,
    pSize,
    qSize,
    inSize = 1

  do {
    p = list
    list = null
    tail = null
    numMerges = 0

    while (p) {
      numMerges++
      q = p
      pSize = 0
      for (i = 0; i < inSize; i++) {
        pSize++
        q = q.nextZ
        if (!q) break
      }

      qSize = inSize

      while (pSize > 0 || (qSize > 0 && q)) {
        if (pSize !== 0 && (qSize === 0 || !q || p.z <= q.z)) {
          e = p
          p = p.nextZ
          pSize--
        } else {
          e = q
          q = q.nextZ
          qSize--
        }

        if (tail) tail.nextZ = e
        else list = e

        e.prevZ = tail
        tail = e
      }

      p = q
    }

    tail.nextZ = null
    inSize *= 2
  } while (numMerges > 1)

  return list
}

// z-order of a point given coords and inverse of the longer side of data bbox
function zOrder(x, y, minX, minY, invSize) {
  // coords are transformed into non-negative 15-bit integer range
  x = 32767 * (x - minX) * invSize
  y = 32767 * (y - minY) * invSize

  x = (x | (x << 8)) & 0x00ff00ff
  x = (x | (x << 4)) & 0x0f0f0f0f
  x = (x | (x << 2)) & 0x33333333
  x = (x | (x << 1)) & 0x55555555

  y = (y | (y << 8)) & 0x00ff00ff
  y = (y | (y << 4)) & 0x0f0f0f0f
  y = (y | (y << 2)) & 0x33333333
  y = (y | (y << 1)) & 0x55555555

  return x | (y << 1)
}

// find the leftmost node of a polygon ring
function getLeftmost(start) {
  let p = start,
    leftmost = start
  do {
    if (p.x < leftmost.x || (p.x === leftmost.x && p.y < leftmost.y)) leftmost = p
    p = p.next
  } while (p !== start)

  return leftmost
}

// check if a point lies within a convex triangle
function pointInTriangle(ax, ay, bx, by, cx, cy, px, py) {
  return (cx - px) * (ay - py) - (ax - px) * (cy - py) >= 0 && (ax - px) * (by - py) - (bx - px) * (ay - py) >= 0 && (bx - px) * (cy - py) - (cx - px) * (by - py) >= 0
}

// check if a diagonal between two polygon nodes is valid (lies in polygon interior)
function isValidDiagonal(a, b) {
  return (
    a.next.i !== b.i &&
    a.prev.i !== b.i &&
    !intersectsPolygon(a, b) && // dones't intersect other edges
    ((locallyInside(a, b) &&
      locallyInside(b, a) &&
      middleInside(a, b) && // locally visible
      (area(a.prev, a, b.prev) || area(a, b.prev, b))) || // does not create opposite-facing sectors
      (equals(a, b) && area(a.prev, a, a.next) > 0 && area(b.prev, b, b.next) > 0))
  ) // special zero-length case
}

// signed area of a triangle
function area(p, q, r) {
  return (q.y - p.y) * (r.x - q.x) - (q.x - p.x) * (r.y - q.y)
}

// check if two points are equal
function equals(p1, p2) {
  return p1.x === p2.x && p1.y === p2.y
}

// check if two segments intersect
function intersects(p1, q1, p2, q2) {
  const o1 = sign(area(p1, q1, p2))
  const o2 = sign(area(p1, q1, q2))
  const o3 = sign(area(p2, q2, p1))
  const o4 = sign(area(p2, q2, q1))

  if (o1 !== o2 && o3 !== o4) return true // general case

  if (o1 === 0 && onSegment(p1, p2, q1)) return true // p1, q1 and p2 are collinear and p2 lies on p1q1
  if (o2 === 0 && onSegment(p1, q2, q1)) return true // p1, q1 and q2 are collinear and q2 lies on p1q1
  if (o3 === 0 && onSegment(p2, p1, q2)) return true // p2, q2 and p1 are collinear and p1 lies on p2q2
  if (o4 === 0 && onSegment(p2, q1, q2)) return true // p2, q2 and q1 are collinear and q1 lies on p2q2

  return false
}

// for collinear points p, q, r, check if point q lies on segment pr
function onSegment(p, q, r) {
  return q.x <= Math.max(p.x, r.x) && q.x >= Math.min(p.x, r.x) && q.y <= Math.max(p.y, r.y) && q.y >= Math.min(p.y, r.y)
}

function sign(num) {
  return num > 0 ? 1 : num < 0 ? -1 : 0
}

// check if a polygon diagonal intersects any polygon segments
function intersectsPolygon(a, b) {
  let p = a
  do {
    if (p.i !== a.i && p.next.i !== a.i && p.i !== b.i && p.next.i !== b.i && intersects(p, p.next, a, b)) return true
    p = p.next
  } while (p !== a)

  return false
}

// check if a polygon diagonal is locally inside the polygon
function locallyInside(a, b) {
  return area(a.prev, a, a.next) < 0 ? area(a, b, a.next) >= 0 && area(a, a.prev, b) >= 0 : area(a, b, a.prev) < 0 || area(a, a.next, b) < 0
}

// check if the middle point of a polygon diagonal is inside the polygon
function middleInside(a, b) {
  let p = a,
    inside = false
  const px = (a.x + b.x) / 2,
    py = (a.y + b.y) / 2
  do {
    if (p.y > py !== p.next.y > py && p.next.y !== p.y && px < ((p.next.x - p.x) * (py - p.y)) / (p.next.y - p.y) + p.x) inside = !inside
    p = p.next
  } while (p !== a)

  return inside
}

// link two polygon vertices with a bridge; if the vertices belong to the same ring, it splits polygon into two;
// if one belongs to the outer ring and another to a hole, it merges it into a single ring
function splitPolygon(a, b) {
  const a2 = new Node(a.i, a.x, a.y),
    b2 = new Node(b.i, b.x, b.y),
    an = a.next,
    bp = b.prev

  a.next = b
  b.prev = a

  a2.next = an
  an.prev = a2

  b2.next = a2
  a2.prev = b2

  bp.next = b2
  b2.prev = bp

  return b2
}

// create a node and optionally link it with previous one (in a circular doubly linked list)
function insertNode(i, x, y, last) {
  const p = new Node(i, x, y)

  if (!last) {
    p.prev = p
    p.next = p
  } else {
    p.next = last.next
    p.prev = last
    last.next.prev = p
    last.next = p
  }

  return p
}

function removeNode(p) {
  p.next.prev = p.prev
  p.prev.next = p.next

  if (p.prevZ) p.prevZ.nextZ = p.nextZ
  if (p.nextZ) p.nextZ.prevZ = p.prevZ
}

function Node(i, x, y) {
  // vertex index in coordinates array
  this.i = i

  // vertex coordinates
  this.x = x
  this.y = y

  // previous and next vertex nodes in a polygon ring
  this.prev = null
  this.next = null

  // z-order curve value
  this.z = null

  // previous and next nodes in z-order
  this.prevZ = null
  this.nextZ = null

  // indicates whether this is a steiner point
  this.steiner = false
}

function signedArea(data, start, end, dim) {
  let sum = 0
  for (let i = start, j = end - dim; i < end; i += dim) {
    sum += (data[j] - data[i]) * (data[i + 1] + data[j + 1])
    j = i
  }

  return sum
}

export {Earcut}
